This is a trial of HIV infected subjects age 6m to 20 yr with documented clinical disease progression while receiving antiretroviral therapy. The combination therapies included ZDV, Videx (ddI) and/or NVP. The objectives compared the antiviral activity of combination therapies as measured by reduction of plasma p24 antigen; compared the relative safety and toxicity of combination therapies and evaluated steady-state ZDV, ddI and NVP pharmacokinetics including potential drug interaction and CSF penetration.